There was a significant heterogeneity between the included studies (small P value of Q-test and large I2 statistic). The results of the statistical tests assessing heterogeneity should be interpreted with caution. When the sample size is small or the number of studies is limited, the Q-test has low statistical power. On the other hand, when the sample size or the number of the included studies is large, the test has high power in detecting a small amount of heterogeneity that may be clinically unimportant [18]. Therefore, a part of observed heterogeneity can be attributed to the number of studies (31 studies) included in the meta-analysis and the large sample size (involving 420,732 participants). However, another part of observed heterogeneity can be attributed to the discrepancies across the studies. The OR estimates of suicidal ideation were reported from 0.5 to 3.10 and that of suicide attempt from 1.65 to 10.50. The source of observed heterogeneity was explored using a meta-regression analysis considering mean age, sex, adjusted/unadjusted effect estimates, and methodological quality of the included studies as covariates. However, none of these
